To refrigerate porthole containers at terminals, a number of mobile or fixed refrigeration units are available in addition to the clip-ons described previously. Each of the tower units shown in Figure 7 can refrigerate two porthole containers, one positioned on each side of the unit. Several of these units can be stacked one on top of the other, allowing tiered stowage. Figure 6, on the other hand, shows a fixed refrigeration plant at the Unikai terminal in Hamburg.
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| Figure 6: Permanently installed refrigeration system for porthole containers at the HHLA Unikai terminal |
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| Figure 7: Tower units used to supply cold air to porthole containers at the HHLA Burchardkai terminal |
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